Cranial Nerves

CHAPTER 15

Cranial Nerves

CLINICAL CASE OLFACTORY NERVE (CN I) OPTIC NERVE (CN II) OCULOMOTOR NERVE (CN III) TROCHLEAR NERVE (CN IV) TRIGEMINAL NERVE (CN V) ABDUCENT NERVE (CN VI) FACIAL NERVE (CN VII) VESTIBULOCOCHLEAR NERVE (CN VIII) GLOSSOPHARYNGEAL NERVE (CN IX) VAGUS NERVE (CN X) SPINAL ACCESSORY NERVE (CN XI) HYPOGLOSSAL NERVE (CN XII) SYNONYMS AND EPONYMS FOLLOW-UP TO CLINICAL CASE QUESTIONS TO PONDER

CLINICAL CASE

A 70-year-old male has excruciating pain in the lower left part of his face. This began 1 month ago. He describes it as being like a jolt of lightning that radiates from his left ear, down to his jaw, and to the side of his mouth. These jolts of pain occur numerous times each day. Between attacks his face seems normal. He denies any numbness or tingling sensations. There is no hearing abnormality. The pain is triggered by talking, chewing, or touch of the lower left part of his face. He is unable to eat or brush his teeth, particularly on the left side, since he fears triggering another painful attack. He can only drink his meals through a straw and cannot lie in bed on his left side. He had the same symptoms about 2 years ago. At that time he was treated with a medication which helped; symptoms subsided, but he stopped taking the medicine. The pain is so distressing that the patient admits to contemplating suicide. The general and neurologic exam is normal, except that he withdraws and will not let anyone touch the left side of his face.

There are 12 pairs of cranial nerves emerging from the brain and radiating from its surface (Fig. 15.1). They pass through skull foramina, fissures, or canals to exit the cranial vault and then distribute their innervation to their respective structures in the head and neck. One of the cranial nerves, the vagus (L.,

“wanderer”) continues into the trunk where it innervates various thoracic and abdominal organs. In addition to being named, the cranial nerves are numbered sequentially with Roman...